The invention relates to a coupling to connect hydraulic pipelines. The coupling has a first coupling part and a second coupling part. The first coupling part includes a first valve received in a housing of the first coupling part and means for receiving the second coupling part. The second coupling part includes a second valve. The first valve includes a valve body which, in the closed position, contacts a sealing face of the housing of the first coupling part. The valve body is axially penetrated by a switching pin. The switching pin is adjustable relative to the valve body towards the second valve. The coupling also includes a switching shaft with an actuating member. The switching shaft is arranged transversely to the valve axis, penetrates the housing of the first coupling part and carries a switching member. The switching member serves to adjust the switching pin and the valve body. For adjustment purposes, the switching member, the valve body and the switching pin include switching faces. The switching pin is loaded towards the switching member by an opening spring supported on the valve body of the first valve. The valve body of the first valve is loaded by a closing spring in the direction of the sealing face of the housing. The loading effect is achieved by actuating the actuating element which, in turn, rotationally adjusts the switching member. The switching pin serves to move the second element into the open position. The housing of the first coupling part is associated with an axially adjustable locking sleeve. The locking sleeve has locking elements which, in the coupled condition, lock the two coupling parts relative to one another. The locking sleeve is transferable, by axial adjustment, into a releasing position.
A coupling is described in DE 43 18 840 C2. A coupling serves to ensure that the two coupling parts do not rest against one another. Thus, oil leakages are reduced to a minimum during the uncoupling operation. This constitutes an advantage compared to couplings described, for example, in ISO 5675 and SAE-J1036 standard, respectively, wherein the sealing cones are extended by a projection which already opens the valves during the coupling operation.
In DE 43 18 840 C2, the switching pin is held in constant contact with the switching member by an opening spring. The switching pin follows the slightest movement of the switching shaft even when the coupling is closed. Furthermore, the switching pin is sealed relative to the valve member of the first coupling part according to rod sealing principles. If the first coupling part is subjected to a static hydraulic pressure, the switching pin is not fully withdrawn by its returning spring. If it is then the intention to couple a pressurized second coupling part, it first has to be ensured, for instance by actuating a control device accordingly, that the first coupling part is depressurized to the extent that the switching pin fully withdraws into the housing. Furthermore, the coupling has to be operated with two hands to connect the coupling parts as well as switch the two switching valves by actuating the actuating element. A certain operating sequence has to be observed. For example, to couple the two coupling parts, it is necessary, first, to transfer the locking sleeve by hand into a releasing position so that the locking elements are able to escape. Once the final coupling position has been reached, the locking sleeve can be released. Under the effect of a spring loading the locking sleeve, the locking sleeve returns into a position where the locking elements engage recesses in the second coupling part to produce a unit. It is only then that the actuating element is actuated to adjust the switching member in order to transfer the two valves into the open position. During the uncoupling operation, first, the switching member has to be transferred into a rotational position which corresponds to the closed position. Subsequently, the coupling sleeve has to be slipped on by hand. The disadvantage is that as a result of the pressure built up in the system, it is necessary to apply high actuating forces.